Bradycardia
Bradycardia refers to a heart rate of less than 60 beats/minute. It occurs normally in young adults, trained athletes, and elderly people as well as during sleep. It’s also a normal response to vagal stimulation caused by coughing, vomiting, or straining during defecation. When bradycardia results from these causes, the heart rate rarely drops below 40 beats/minute. However, when it results from pathologic causes (such as cardiovascular disorders), the heart rate may be slower. (See Managing severe bradycardia, page 102.)
History
After detecting bradycardia, check for related signs of life-threatening disorders. If the patient’s bradycardia isn’t accompanied by unfavorable signs, ask the patient if he or a family member has a history of a slow pulse rate because this may be inherited. Also, find out if he has an underlying metabolic disorder such as hypothyroidism which can precipitate bradycardia. Ask which medications he’s taking and if he’s complying with the prescribed schedule and dosage.
Physical assessment
Monitor vital signs, temperature, pulse, respirations, blood pressure, and oxygen saturation. Then perform a complete cardiac assessment.
Medical causes
Cardiac arrhythmia
Depending on the type of cardiac arrhythmia and the patient’s tolerance of it, bradycardia may be transient or sustained, benign, or life-threatening. Related findings result from reduced cardiac output and include hypotension, palpitations, dizziness, weakness, dyspnea, chest pain, decreased urine output, altered level of consciousness (LOC), syncope, and fatigue.
Cardiomyopathy
Cardiomyopathy, a potentially life-threatening disorder, may cause transient or sustained bradycardia. Other findings include dizziness, syncope, edema, fatigue, jugular vein distention, orthopnea, dyspnea, and peripheral cyanosis.
Cervical spinal injury
Bradycardia associated with a cervical spinal injury may be transient or sustained, depending on the severity of the injury. Its onset coincides with sympathetic denervation. Associated signs and symptoms of cervical spinal injury include hypotension, decreased body temperature, slowed peristalsis, leg paralysis, and partial arm and respiratory muscle paralysis.
Hypothermia
When core body temperature drops below 89.6° F (32° C), causing hypothermia, bradycardia usually appears. It’s accompanied by shivering, peripheral cyanosis, muscle rigidity, bradypnea, and confusion leading to stupor. If the core temperature drops below 86° F (30° C), the patient may appear dead (in a state of rigor mortis) with no palpable pulse or audible heart sounds.
Hypothyroidism
Hypothyroidism causes severe bradycardia in addition to fatigue, constipation, unexplained weight gain, and sensitivity to cold. Related signs include cool, dry, thick skin; sparse, dry hair; facial swelling; periorbital edema; thick, brittle nails; and confusion leading to stupor.
Myocardial infarction
Sinus bradycardia is the arrhythmia most commonly associated with acute myocardial infarction (MI). Accompanying signs and symptoms of an MI include an aching, burning, or viselike pressure in the chest that may radiate to the jaw, shoulder, arm, back, or epigastric area; nausea and vomiting; cool, clammy, and pale or cyanotic skin; anxiety; and dyspnea. Blood pressure may be elevated or depressed. Auscultation may reveal abnormal heart sounds.
Other causes
Diagnostic tests
Cardiac catheterization and electrophysiologic studies can induce temporary bradycardia.
Drugs
Beta-adrenergic blockers and some calcium channel blockers, cardiac glycosides, topical miotics (such as pilocarpine), protamine, quinidine and other antiarrhythmics, and sympatholytics may cause transient bradycardia. Failure to take thyroid replacements may cause bradycardia.
Invasive treatments
Suctioning can induce hypoxia and vagal stimulation, causing bradycardia. Cardiac surgery can cause edema or damage to conduction tissues, causing bradycardia.
Special considerations
Continue to monitor vital signs frequently. Be especially alert for changes in cardiac rhythm, respiratory rate, and LOC.
Prepare the patient for laboratory tests, which can include complete blood count; cardiac enzyme, serum electrolyte, blood glucose, blood urea nitrogen, arterial blood gas, and blood drug levels; thyroid function tests; and a 12-lead electrocardiogram. If appropriate, prepare the patient for 24-hour Holter monitoring.
Pediatric pointers
Heart rates are normally higher in children than in adults. Fetal bradycardia — a heart rate of less than 120 beats/minute — may occur during prolonged labor or complications of delivery, such as compression of the umbilical cord, partial abruptio placentae, and placenta previa. Intermittent bradycardia, sometimes accompanied by apnea, commonly occurs in premature infants. Bradycardia rarely occurs in full-term infants or children. However, it can result from congenital heart defects, acute glomerulonephritis, and transient or complete heart block associated with cardiac catheterization or cardiac surgery.
Geriatric pointers
Sinus node dysfunction is the most common bradyarrhythmia encountered among elderly patients. Patients with this disorder may have as their chief complaint fatigue, exercise intolerance, dizziness, or syncope. If the patient is asymptomatic, no intervention is necessary. Symptomatic patients, however, require careful scrutiny of their drug therapy. Beta-adrenergic blockers, verapamil, diazepam, sympatholytics, antihypertensives, and some antiarrhythmics have been implicated; symptoms may clear when these drugs are discontinued. Pacing is usually indicated in patients with symptomatic bradycardia lacking a correctable cause.
Patient counseling
Discuss signs and symptoms to report, such as light-headedness or syncope. Teach the patient to take his pulse and make sure he knows parameters for calling the physician and seeking emergency care. If the patient had a pacemaker inserted, provide instructions for its use.
Pictures
Book Source Details
- Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 Lippincott Williams & Wilkins.
Other Book Chapters Related to Slow heartbeat
Read excerpts from these other book chapters related to Slow heartbeat:
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- "Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series" (2007)
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- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
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- "Nursing: Interpreting Signs and Symptoms" (2007)
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Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2008 Williams & Wilkins.
More About Causes of Slow heartbeat
» Next page: Heart Murmurs (Asymptomatic) (The Diagnostic Approach to Symptoms and Signs in Pediatrics)
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